Oh wow, there are a ton of plate configurationsout there.
www.hydrogengarage.com is a good place to go for info and a lot of links. I been lookin at youtube and see a lot of work with helix shaped electrodes that seem to yield a lot of gas, saw one vid that claimed a gent went from 26 to 44 mpg on his new mercury Milan with no other alterations, an escort that gets 60mpg. From what I can see once one builds the basic pvc canister the sky is the limit on electrode configuation inside. On the Hydrogen garage site they talk about nuetral plates with are plates between charged plates that seem to lower the amperage going thru the cell and lengthen the time between cleanings. I have to say I am very interested in this also.